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How a heat pump works

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Re: How a heat pump works

#271

Post by rainsford »

Casteil wrote: post #222
yreg wrote: post #6

Technology Connections has a good video on heat pumps. (Actually several of them, I link the newest one.) https://www.youtube.com/watch?v=MFEHFsO-XSI

He does, but he omits a lot of important considerations that make heat pumps impractical for normal Americans. If he touches on them, it's briefly - if at all, e.g.: - More expensive units, and more expensive to run power wise. It's always difficult to get adoption of new technology that's "better" but more expensive to buy & repair - to the point where RoI may never happen. - Power grid implications during very low/…

> He does, but he omits a lot of important considerations that make heat pumps impractical for normal Americans.

Some form of this comment always comes up in these heat pump threads, and I never understand the idea that heat pumps are some elite affectation that doesn't make sense for anyone else. Many millions of Americans live in parts of country where it gets warm enough in the summer to justify central air conditioning and chilly enough in the winter that you need heat but the heating source doesn't need to handle super low temps on a regular basis.

A heat pump is literally one of the simplest ways to address the year round climate control needs for those people since it's a single system that handles both heating and cooling with only marginally more complexity than the air conditioner you'd want anyways. Throw in electric backup heat, which is probably the simplest backup and keeps the system all-electric, and you have a system able to handle a pretty broad range of temperatures all year. As heat pump technology gets better, the applicable temperature range gets colder and colder and makes heat pumps practical for a wider range of "normal Americans".

This isn't just theoretical. Heat pumps account for 17% of heating systems in the US, which isn't huge, but over 40% in North Carolina, South Carolina, and Alabama and a significant percentage in many other states as well. Obviously there are cases where heat pumps are at least currently impractical given the construction, climate, etc, but dismissing them as some effete toy seems a bit silly.

Edit: Interestingly, most states seem to have a significantly higher percentage of homes with electricity as their primary heating fuel than they do homes with heat pumps, suggesting a lot of homes with things like electric baseboard heating. While not all of those homes necessarily have central AC, using Georgia as an example, 85% of homes have central AC and 53% use electricity as their main heating fuel, while only 29% have heat pumps. That suggests quite a few homes with central AC that use electric baseboard or similar. Heat pumps for those homes seem like they'd be very practical.

Re: How a heat pump works

#272

Post by snozolli »

Casteil wrote: post #222
yreg wrote: post #6

Technology Connections has a good video on heat pumps. (Actually several of them, I link the newest one.) https://www.youtube.com/watch?v=MFEHFsO-XSI

He does, but he omits a lot of important considerations that make heat pumps impractical for normal Americans. If he touches on them, it's briefly - if at all, e.g.: - More expensive units, and more expensive to run power wise. It's always difficult to get adoption of new technology that's "better" but more expensive to buy & repair - to the point where RoI may never happen. - Power grid implications during very low/…

With a heat pump, you -need- an alternative source of heat - since some days when it's particularly cold

Modern heat pumps redirect some heat to prevent the coils from freezing. What you wrote is common FUD pushed by the oil & gas companies.

That said, you'd be a fool to live in an area with life-threateningly low temperatures and not have a backup heat source.

Re: How a heat pump works

#273

Post by snozolli »

peterhunt wrote: post #180
boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

It is coordinated. In many states there are huge incentives [1] to disconnect your existing home from (and not connect new construction to) the natural gas infrastructure. This is great for the climate but air source heat pump technology simply doesn't work well in cold climates. Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency." What most people d…

Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency."

Most things that are already installed are worse than the latest technology that's available.

That's not an argument against the latest technology.

Re: How a heat pump works

#274

Post by gambiting »

Casteil wrote: post #248
nly wrote: post #225

Earlier quoted context omitted.

- Better than resistive electric heating for the grid. Gas is going away so this is a problem that has to be solved anyway. - Economies or scale will solve the repair and maintenance burden... hell, it's not like a gas boiler is maintenance free...fucking things requiring serving every year and break down all the time in the UK. - almost noone has a generator when the power goes out anyway. This is a very wealthy Ame…

- Sure, at least when it's not super cold. Electrical grid may be a "problem that has to be solved" but it's one that carries staggering price tags and will have to be gradually transitioned into over decades. Natural gas will likely still be used as a heat source for many well into the late this century if not longer. - Gas boilers are far simpler units. Less moving parts, simpler electronics, all in all fewer point…

>> all in all fewer points of failure than a cutting edge heat pump that can actually produce heat when it's below 20f (-7c, i.e. the only kind of heatpump that might stand a chance at heating throughout the cold winters most of the northern US gets).

My family has one in Poland, it was -20C this winter already and it worked absolutely fine. It's some cheap unit, wouldn't call it "cutting edge". I think there's a simple resistive heater that de-ices the fins at low temps, but it kept the interior of the house at a (very toasty) 24C pretty much non stop even in those low temperatures. I have no idea why people keep saying heat pumps don't work in low temps. I had a basic split unit fitted to my home in UK, literally a basic £600 midea unit and apparently it should work down to -25C without any problem.

>>Gas boilers are far simpler units. Less moving parts, simpler electronics

Have you ever looked inside a modern gas boiler??? I hard disagree that it has less parts than a modern heat pump. A heat pump is like your fridge - there's an inverter, compressor, and a whole bunch of fins, that's about it. A gas boiler has multiple tanks, burn chamber, exhaust recirculation, at least 5-6 probes to measure every part of the process(and they all can fail in surprising ways that renders your boiler dead).

Re: How a heat pump works

#275

Post by ryantgtg »

Casteil wrote: post #222
yreg wrote: post #6

Technology Connections has a good video on heat pumps. (Actually several of them, I link the newest one.) https://www.youtube.com/watch?v=MFEHFsO-XSI

He does, but he omits a lot of important considerations that make heat pumps impractical for normal Americans. If he touches on them, it's briefly - if at all, e.g.: - More expensive units, and more expensive to run power wise. It's always difficult to get adoption of new technology that's "better" but more expensive to buy & repair - to the point where RoI may never happen. - Power grid implications during very low/…

Just to soften a few of your confident declarations.

> normal Americans

Please revise this phrase. America consists of many different climates and it's very unclear what you mean or why you chose the word "normal."

> More expensive to run power wise

You're comparing new gas HVAC vs new heat pump. However, don't forget about all the folks that are purchasing a heat pump to replace an existing gas unit! For example, my gas unit (Goodman unit used in California) is old and not even energy star compliant! A new heat pump will be more efficient.

> With a heat pump, you -need- an alternative source of heat

By 'you' are you referring to me (or, say, the ~7% of the US population that lives in my small area of the country)? If so, that's not true! It doesn't get too cold here. And I reckon there are quite a few areas in this country where it doesn't get cold enough for a heat pump to eat shit.

When you refer to prices and returns on investment, are you using a unit + professional installation cost (like $18k+ or something)? Or the unit itself (~$4.5k) plus perhaps a DIY installation costs (~$1.5-2k)? There is a big range there in costs, and the ROI is dependent on that.

Re: How a heat pump works

#276

Post by gambiting »

mytailorisrich wrote: post #126
Thlom wrote: post #95

Earlier quoted context omitted.

I replaced my old air-to-air heat pump with a new one last year. Cost me in total around $3000-$4000. Might have been a bit more expensive if it was a completely new install depending on how it would be installed, but not too much more expensive. Might be more expensive in countries where you are using gas boilers as it sounds like your heating setup is much more complex than where I live.

Here in the UK, I think the cost of installing a new heat pump, bearing in mind that it's an installation from scratch, starts at about £10k ($12k as today's rate) to several tens of thousands. A ground source heat pump (which seem to be the ones pushed by the gov?) is probably £15k to £30k if you can install one at all. Replacing an existing gas boiler, which is what most people have, is probably around £2k or even…

Which I absolutely don't get. I just had a mini split unit installed at our house here in North East, paid £1500 total with installation, and damn that thing throws a lot of heat - I literally stopped using our gas boiler, it's more efficient(and cheaper!!!!) to use this unit for heating than to burn gas. It uses like 800W of power when running but produces ~4kW of heat.

I imagine the "proper" heat pump costs a lot because it has to integrate into your central heating - heat and pump water etc. But I also imagine for a lot of people in this country 2-3 mini splits like this one would be absolutely sufficient, wouldn't cost a fortune, and would save them money(plus they can be used for cooling when needed).

Re: How a heat pump works

#277

Post by rgmerk »

Casteil wrote: post #248
nly wrote: post #225

Earlier quoted context omitted.

- Better than resistive electric heating for the grid. Gas is going away so this is a problem that has to be solved anyway. - Economies or scale will solve the repair and maintenance burden... hell, it's not like a gas boiler is maintenance free...fucking things requiring serving every year and break down all the time in the UK. - almost noone has a generator when the power goes out anyway. This is a very wealthy Ame…

- Sure, at least when it's not super cold. Electrical grid may be a "problem that has to be solved" but it's one that carries staggering price tags and will have to be gradually transitioned into over decades. Natural gas will likely still be used as a heat source for many well into the late this century if not longer. - Gas boilers are far simpler units. Less moving parts, simpler electronics, all in all fewer point…

88% of US households already have heat pumps, and 66% of households have centralised heat pump systems - otherwise known as air conditioning.

If you can afford to have them just for cooling, you can afford to have them for heating as well; in fact, the capital cost may well be lower if people just used their air conditioning systems to heat as well.

The same goes for reliability - we manage to make air conditioning acceptably reliable and the tech is basically the same.

Re: How a heat pump works

#278

Post by peterhunt »

snozolli wrote: post #273
peterhunt wrote: post #180

Earlier quoted context omitted.

It is coordinated. In many states there are huge incentives [1] to disconnect your existing home from (and not connect new construction to) the natural gas infrastructure. This is great for the climate but air source heat pump technology simply doesn't work well in cold climates. Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency." What most people d…

Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency." Most things that are already installed are worse than the latest technology that's available. That's not an argument against the latest technology.

I’m talking about the ones sold in the United States in the last few years. Mine is a Carrier manufactured in 2022

Re: How a heat pump works

#279

Post by peterhunt »

nicpottier wrote: post #184
peterhunt wrote: post #180

Earlier quoted context omitted.

It is coordinated. In many states there are huge incentives [1] to disconnect your existing home from (and not connect new construction to) the natural gas infrastructure. This is great for the climate but air source heat pump technology simply doesn't work well in cold climates. Most heat pumps in the United States have 100% efficiency down to about 20 degrees F. Below that they "lose efficiency." What most people d…

This is FUD. I live in climate zone 5 in a 100 year old house that has high heating demands and our air source heat pump has been awesome, even when it dipped into the negatives briefly this year. Our heat pump is over 100% efficient down to 0F.

What type of heat pump do you have out of curiosity?

Re: How a heat pump works

#280

Post by timerol »

Bhilai wrote: post #26

Definitely a lot of posts about heat pumps on HN recently that this topic has piqued my interest but only to the point that I want to know if I can install one in my home. Are there any legit resources out there that can help me understand if heat pump is a right choice for my home based on Geo, type of home, sqft and other factors to consider before replacing current systems (two ACs and two furnaces?)

What climate zone are you in? (assuming US) https://learnmetrics.com/wp-content/uploads/hspf4-and-hspf5-...

If you're in 1, 2, or 3, heat pumps are definitely the right option. In zone 4 or 5, newer cold temperature heat pumps are a good idea. In 6, 7, or 8 it's less of a sure thing, and you will likely want a backup source for the colder days.

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